1. Field of the Invention
The present invention relates to photosensitive paste compositions, to barrier ribs of plasma display panels (PDPs) including the same and to PDPs including the barrier ribs.
2. Description of the Related Art
FIG. 1 illustrates a typical plasma display panel (PDP). Referring to FIG. 1, a PDP includes a front panel 110 and a rear panel 120. The front panel 110 includes a front substrate 111; sustain electrode pairs 114 formed on a rear surface 111a of the front substrate 111, where each sustain electrode pair 114 includes a Y electrode 112 and an X electrode 113; a front dielectric layer 115 covering the sustain electrode pairs; and a protective layer 116 covering the front dielectric layer 115. The Y electrode 112 and the X electrode 113 include transparent electrodes 112b and 113b respectively, where the transparent electrodes 112b and 113b are made of ITO, etc.; and bus electrodes 112a and 113a, each including a black electrode (not shown) for contrast enhancement and a white electrode (not shown) for imparting conductivity. The bus electrodes 112a and 113a are connected to connection cables disposed on the left and right sides of the PDP.
The rear panel 120 includes a rear substrate 121; address electrodes 122 formed on a front surface 121a of the rear substrate 121 which intersect the sustain electrode pairs; a rear dielectric layer 123 covering the address electrodes; a barrier rib 124 formed on the rear dielectric layer 123 to partition discharge cells 126; and a phosphor layer 125 disposed in each discharge cell. The address electrodes are connected to connection cables disposed on upper and lower sides of the PDP.
In PDPs, barrier ribs are structures formed on the rear panel (or rear substrate), which define discharge spaces and prevent electrical or optical crosstalk between adjacent discharge cells. Such barrier ribs have various shapes (e.g. stripes or matrices) and sizes (i.e., width and pitch) depending on the type of PDP.
The barrier ribs are formed on the dielectric layer covering the address electrodes on the lower substrate of the PDP using a screen printing method, a sand blasting method, etching, photolithography, or the like.
When forming a barrier rib using a screen printing method, a barrier rib paste for printing is printed on a substrate using a patterned mask and a squeegee and then dried to remove solvent. The printing and drying are repeated several times to obtain a film with a desired thickness. The obtained film is sintered to thereby form a barrier rib. However, this method is time-consuming, and makes it difficult to form a uniformly patterned barrier rib due to misalignment and repeated printing, and the resulting barrier rib has low resolution.
When forming a barrier rib using a sand blasting method, a barrier rib paste is printed once on a substrate by a table coater and then dried to obtain a film with a desired thickness. A dry film resist with sanding resistance is then laminated on the film and patterned through exposure to light and development. Then, micro-abrasive sandblasting is performed under high pressure using the dry film resist pattern as a mask to obtain a patterned film. The residual dry film resist is removed and the patterned film is sintered to complete a barrier rib. Although a barrier rib formed by sandblasting has higher resolution than one formed by screen printing, the sandblasting method is a complicated process and causes damage to electrode terminals due to collision with abrasive sand.
Etching is a similar to sand blasting. However, unlike in sand blasting, in etching, a barrier rib is formed by pattering a sintered membrane using an etching solution. Using the etching method, high resolution can be obtained, but the manufacturing cost is high.
When forming a barrier rib using photolithography, a photosensitive paste is printed and dried to form a film with a desired thickness. The film is exposed to UV light by a UV exposure system equipped with a photomask. The printing, drying, and exposure are repeated several times. Development is then performed to selectively remove an unexposed region. Sintering is then performed to obtain a barrier rib. Photolithography can form a barrier rib with higher resolution than that formed by screen printing. Also, unlike sandblasting, photolithography does not require a dry film resist and a sanding process. However, photolithography requires many processes and misalignment occurs due to the repeated processes.
To address these problems, a method has been proposed to minimize the difference between the refractive indices of an organic component and an inorganic component by using an organic component having a high refractive index and an inorganic component having a low refractive index. This minimizes the number of preparation processes. However, the binder used in such a method includes an aromatic group and a Br atom to obtain the high refractive index. These materials have bad pyrolytic properties and are harmful to the human body. The binder also includes a cross-linking agent having a high refractive index, which includes a S atom, and thus is difficult to be synthesized and is expensive.